Use variable in re.sub, for Python parsing multiple datetime-format strings?

问题

I'm trying to come up with a function to translate various human date/time-format strings to Python compatible ones (from '*yyyy-MMM-dd*' to '*%Y-%b-%d*').

So far I built the translate dictionary below (a list of tuples [('yyyy','%Y'),('MMM','%b'),...]) so I can convert placeholder fields in input format-strings into strptime '%x' fields e.g.:

'yyyy-MMM-dd' --> '{5}-{3}-{12}'

But what do I do next? I've tried multiple ways:

>>> re.sub('({\d+})',translateList['\1'][1],'{5}-{3}-{12}')
TypeError: list indices must be integers, not str

>>> re.sub('({\d+})',translateList[int('\1')][1],'{5}-{3}-{12}')
ValueError: invalid literal for int() with base 10: '\x01'

>>> re.sub('({\d+})',translateList[eval('\1')][1],'{5}-{3}-{12}')
SyntaxError: unexpected EOF while parsing

How do I pass what matched into the list? Or any other way to so this?

EDIT: My current approach is this, not fully satisfied:

def _getDatetimeFormatStringFromMuggleString(input):
    muggleList = [
        ('yyyy','%Y'), ('yy','%Y'),                             # year
        ('MMMM','%B'), ('MMM','%b'), ('MM','%m'), ('M','%m'),   # Month
        ('dddd','%A'), ('ddd','%a'), ('dd','%d'), ('d','%d'),   # day
        ('HH','%H'), ('H','%H'), ('hh','%I'), ('h','%I'),       # hour
        ('mm','%M'), ('m','%M'),                                # minute
        ('ss','%S'), ('s','%S'),                                # second
        ('tt','%p'), ('t','%p'),                                # AM/PM
    ]

    for i in muggleList:
        if i[0] in input and '%'+i[0] not in input:
            input = input.replace(i[0], i[1])

    return input

回答1:

Why roll your own when you can use dateutil.parser?

import dateutil
outdate = dateutil.parser.parse(instr, yearfirst=True)

回答2:

Why don't you use strptime:

>>> from datetime import datetime
>>> datetime.strptime('2012-12-12', '%Y-%j-%d')
datetime.datetime(2012, 1, 12, 0, 0)

来源：https://stackoverflow.com/questions/18768412/use-variable-in-re-sub-for-python-parsing-multiple-datetime-format-strings

标签

python

regex

dynamic

datetime-format

date-parsing